Methods and apparatuses for controlling angular orientations of a person support apparatus

ABSTRACT

A method for controlling an angular orientation of a person support apparatus including a bladder portion containing fluidized particulate material, an upper frame, and a base frame may include adjusting a height of the upper frame with respect to the base frame with at least one of a first and second actuator at respective speeds, determining a dynamic angular orientation of the upper frame with respect to the base frame based on at least one of a respective operating characteristic of the first and second actuator, determining a corrected angular orientation based on the dynamic angular orientation and a floor angle indicative of the orientation of the base frame with respect to horizontal, comparing the corrected angular orientation with an orientation reference range, and adjusting at least one actuator speed when the corrected angular orientation is outside the orientation reference range until it is within the orientation reference range.

CROSS REFERENCE To RELATED APPLICATIONS

The present specification claims priority to U.S. Provisional PatentApplication Ser. No. 62/182,045, filed Jun. 19, 2015 and entitled“METHODS AND APPARATUSES FOR CONTROLLING ANGULAR ORIENTATIONS OF APERSON SUPPORT APPARATUS,” the entirety of which is incorporated byreference herein.

TECHNICAL FIELD

The present specification generally relates to person supportapparatuses for use in healthcare facilities and, more specifically, toperson support apparatuses with angular orientation control systems andmethods for operating the same.

BACKGROUND

Individuals in health care facilities may rest on person supportapparatuses that include mattress replacement systems having bladderscontaining particulate material. Varying weights across such individualsmay affect a distribution of the particulate material, such as duringseating and/or during raising or lowering a height of such personsupport apparatuses.

Accordingly, a need exists for alternative methods for controlling andadjusting the angular orientation of portions of the person supportapparatuses, whereby a desired distribution of the particulate materialsis maintained.

SUMMARY

In one embodiment, a method for controlling an angular orientation of aperson support apparatus including a support surface having a bladderportion containing fluidized particulate material, an upper frame, and abase frame may include adjusting a height of the upper frame withrespect to the base frame with at least one of a first actuator and asecond actuator at respective first and second actuator speeds. Themethod may further include determining a dynamic angular orientation ofthe upper frame with respect to the base frame based on at least one ofan operating characteristic of the first actuator and an operatingcharacteristic of the second actuator, and determining a correctedangular orientation based on the dynamic angular orientation and a floorangle indicative of the orientation of the base frame with respect tohorizontal. The method may further include comparing the correctedangular orientation with an orientation reference range, and adjustingat least one of the first actuator speed and the second actuator speedwhen the corrected angular orientation is outside the orientationreference range until the corrected angular orientation is within theorientation reference range.

In another embodiment, a method for controlling an angular orientationof a person support apparatus that includes a support surface having abladder portion containing fluidized particulate material may includeactuating at least one of a first actuator and a second actuator,respectively coupled to the person support apparatus at a first end anda second end, at a respective first actuator speed and a second actuatorspeed to raise or lower a height of the person support apparatus, andreceiving a first reading indicative of a first angular orientation ofthe first end of the person support apparatus with respect to the secondend and relative to horizontal. The first reading may be at leastgenerated from a first sensor and a second sensor respectivelyassociated with the first actuator and the second actuator. The methodmay further include determining a corrected first reading indicative ofthe first angular orientation based on the first reading and acalibration of the person support apparatus, comparing the correctedfirst reading and an orientation reference range, and actuating at leastone of the first actuator and the second actuator automatically at adifferent speed when the corrected first reading is outside theorientation reference range until an adjusted corrected first readingindicative of an adjusted first angular orientation is within theorientation reference range.

In yet another embodiment, a system for controlling an angularorientation of a person support apparatus may include at least a firstactuator associated with a head end as a first end and a second actuatorassociated with a foot end as a second end of the person supportapparatus, and an electronic control unit comprising a processorcommunicatively coupled to a non-transitory computer storage medium. Thenon-transitory computer storage medium stores instructions that may,when executed by the processor, cause the processor to: actuate at leastone of the first actuator and the second actuator at a respective firstactuator speed and a second actuator speed to raise or lower a height ofthe person support apparatus, and receive, automatically with theelectronic control unit, a first reading indicative of a first angularorientation of the first end of the person support apparatus withrespect to the second end and relative to horizontal, wherein the firstreading is generated from a first sensor and a second sensorrespectively associated with the first actuator and the second actuator.The non-transitory computer storage medium stores instructions that may,when executed by the processor, further cause the processor to:determine, automatically with the electronic control unit, a correctedfirst reading indicative of the first angular orientation based on thefirst reading and a calibration of the person support apparatus,compare, automatically with the electronic control unit, the correctedfirst reading and an orientation reference range, and actuate at leastone of the first actuator and the second actuator, automatically withthe electronic control unit, at a different speed when the correctedfirst reading is outside the orientation reference range until anadjusted corrected first reading indicative of an adjusted first angularorientation is within the orientation reference range.

In yet another embodiment, a method for controlling an angularorientation of a person support apparatus including a base frame, anupper frame positioned on the base frame, a support surface having abladder portion containing fluidized particulate material positioned onthe upper frame, and a torso frame positioned on the upper frame mayinclude receiving a head of bed (HOB) angle indicative of an angularorientation of the torso frame with respect to the upper frame, andreceiving a weight of a person positioned on the person supportapparatus. The method may further include determining a tilt angle ofthe upper frame with respect to the base frame based on the HOB angleand the weight of the person positioned on the person support apparatus,and adjusting an angular orientation of the upper frame with respect tothe base frame until the upper frame is oriented at the tilt angle withrespect to the base frame. The tilt angle may correspond to a minimumdepth of the fluidized particulate material at a point of maximumimmersion of the person on the bladder portion of the support surface.

These and additional features provided by the embodiments describedherein will be more fully understood in view of the following detaileddescription, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 schematically depicts a person support apparatus, according toone or more embodiments shown and described herein;

FIG. 2 schematically depicts an exploded view showing the upper frameand the lower frame of the person support apparatus of FIG. 1, accordingto one or more embodiments shown and described herein;

FIG. 3 schematically depicts an exemplary control box of the personsupport apparatus of FIG. 1, according to one or more embodiments shownand described herein;

FIG. 4 schematically depicts an exemplary angle and height control panelof the person support apparatus of FIG. 1, according to one or moreembodiments shown and described herein;

FIG. 5 schematically depicts an exemplary pendant of the person supportapparatus of FIG. 1, according to one or more embodiments shown anddescribed herein;

FIG. 6 schematically depicts another person support apparatus, accordingto one or more embodiments shown and described herein;

FIG. 7A schematically depicts a top view of the mattress system of theperson support apparatus of FIG. 6, according to one or more embodimentsshown and described herein;

FIG. 7B schematically depicts an elevation view of the mattress systemof the person support apparatus of FIG. 6 with a foot end level with aseat end, according to one or more embodiments shown and describedherein;

FIG. 7C schematically depicts an elevation view of the mattress systemof the person support apparatus of FIG. 6 with a foot end disposed abovea seat end, according to one or more embodiments shown and describedherein;

FIG. 7D schematically depicts an elevation view of the mattress systemof the person support apparatus of FIG. 6 with a foot end disposed belowa seat end, according to one or more embodiments shown and describedherein;

FIG. 8 schematically depicts a system for implementing a method tocontrol angular orientations of two portions of a person supportapparatus, according to one or more embodiments described herein;

FIG. 9 schematically depicts a flow chart of a method to control angularorientations of a portion of a person support apparatus, according toone or more embodiments described herein;

FIG. 10 is a graphical depiction of the immersion depth (y-axis) as afunction of person weight showing a relationship between head of bed(“HOB”) angle, person weight, and depth of immersion with respect to afluidized particulate material disposed in a bladder portion of thesupport surface;

FIG. 11 is a graphical depiction of a regression analysis of data withrespect to a HOB angle of 0°, according to one or more embodimentsdescribed herein;

FIG. 12 is a graphical depiction of a regression analysis of data withrespect to a HOB angle of 30°, according to one or more embodimentsdescribed herein;

FIG. 13 is a graphical depiction of a regression analysis of data withrespect to a HOB angle of 45°, according to one or more embodimentsdescribed herein;

FIG. 14 is a graphical depiction of a regression analysis of data withrespect to a HOB angle of 60°, according to one or more embodimentsdescribed herein;

FIG. 15 illustrates an example TABLE 1 setting forth data with respectto different HOB angles and the resultant maximum supportable weightsfor different tilt angles of the support surface;

FIG. 16 illustrates an example TABLE 2 setting forth mean slope data atleast partially based on the linear relationships of FIGS. 10-14,according to one or more embodiments described herein; and

FIG. 17 illustrates an example TABLE 3 setting forth data calculatedwith EQUATION 1 to estimate depth of immersion in inches as a functionof HOB and person weight along with a comparison to empirically deriveddata.

DETAILED DESCRIPTION

A person support apparatus may include a support surface having abladder portion containing particulate material and a fluidizationsystem for injecting fluid into the bladder portion and fluidizing theparticulate material. An electronic control unit may control the angularorientation of one or more ends of the person support apparatus suchthat the fluidized particulate material contained within the bladderportion of the person support apparatus is distributed in the bladderportion. Otherwise, if the fluidized particulate material does notremain distributed when the person support apparatus is moved upwards ordownwards, for example, the fluidized particulate material might migratedue to a gravitational pull toward an end of the person supportapparatus, such as when the person support apparatus is placed upon onan angled floor causing a person resting on the support surface to beinadequately supported. As will be described in greater detail herein,factors that may affect such migration and a maximum amount of weightthat the fluidized particulate material may support include a tilt angleassociated with the support surface.

The methods and apparatuses described herein may be used to maintain aperson support apparatus within an orientation reference range as theheight of the person support apparatus is adjusted so that the fluidizedparticulate material contained within the bladder portion of the personsupport apparatus has a desired distribution during and after the heightadjustments. Methods and apparatuses for controlling angularorientations of person support apparatuses, such as in acute caresettings, to maintain the fluidized particulate material in a specificdistribution in the bladder portion during movement of the personsupport apparatus are further described herein with specific referenceto the appended drawings.

FIG. 1 schematically depicts one embodiment of a person supportapparatus 10 with an angular orientation control system which may beused in, for example, an acute care setting, such as a hospital. Theperson support apparatus 10, for example, may be a person supportapparatus similar to the HILL-ROM® CLINITRON® RITE HITE® Air FluidizedTherapy bed or the HILL-ROM® ENVELLA™ Air Fluidized Therapy System bed,which are commercially available from Hill-Rom Services, Inc. ofBatesville, Ind. However, it should be understood that other personsupport apparatuses compatible with the methods described herein arecontemplated and possible.

The person support apparatus 10 generally includes a base frame 101 andan upper frame 102 on which a mattress system 104 is supported. The baseframe 101 supports the person support apparatus 10 on the floor 500 andmay include wheels 6, such as casters, to facilitate relocating and/orrepositioning the person support apparatus 10 on the floor 500. Theupper frame 102 is coupled to the base frame 101 with pivoting linkages3, 5 which facilitate raising and lowering (e.g., transitioning) theupper frame 102 with respect to the base frame 101 as indicated by arrow600 and described in greater detail herein. More particularly, a firstend of linkage 3 is pivotally coupled to the base frame 101 and a secondend of linkage 3 is pivotally coupled to the upper frame 102. Similarly,a first end of linkage 5 is pivotally coupled to the base frame 101 anda second end of linkage 5 is pivotally coupled to the upper frame 102.

Still referring to FIG. 1, in embodiments, the person support apparatus10 may include a torso frame 109 which is pivotally coupled to the upperframe 102. The torso frame 109 may be pivoted with respect to the upperframe 102 thereby facilitating increasing an angle of inclination of themattress system 104 proximate the head end 122 of the person supportapparatus 10. In embodiments, a torso actuator 95 (FIG. 2) may becoupled to the upper frame 102 and the torso frame 109 to facilitatepivoting the torso frame 109 with respect to the upper frame 102 via anelectronic control unit. The mattress system 104 includes an upperportion 130 and a lower portion 140. The upper portion 130 of themattress system 104 is positioned on the torso frame 109. In someembodiments, the upper portion 130 of the mattress system 104 maygenerally include one or more fluid bladders 131 which may be inflatedor deflated to adjust the position of a person on the mattress system104 and/or increase or decrease the firmness of a portion of themattress system 104 according to the person's preference.

Further, the lower portion 140 the mattress system 104 of the personsupport apparatus 10 includes a fluidized bed 112 of particulatematerial contained within a bladder portion 110 positioned in a tubportion 115. The particulate material may be, for example, microspheres(i.e., beads) formed from glass, plastic, and/or ceramic materials. Afluidization system (not shown), such as a pump, may be used to pump afluid, such as a gas or air, into the particulate material containedwithin the bladder portion, thereby fluidizing the particulate materialand creating the fluidized bed 112 in the lower portion 140 of themattress system 104. The fluidized bed 112 assists in distributing andredistributing pressure against the skin of a person positioned on themattress system 104.

In embodiments, the person support apparatus 10 further includes acontrol box 24 and an angle and height control panel 26. In theembodiment shown in FIG. 1, the control box 24 and the control panel 26are located on a footboard 25 coupled to the upper frame 102 at the footend 120 of the person support apparatus 10. The person support apparatus10 also includes side rails 27A, 27B coupled to the upper frame 102along the sides of the mattress system 104 between the foot end 120 andthe head end 122 of the person support apparatus 10. A side rail 27B mayinclude a pendant 28 to further provide person-accessible controlfeatures to a user to allow for adjustment of the person supportapparatus 10, as described in greater detail herein. The person supportapparatus may further include a foot control 29 for controlling certainfunctions of the person support apparatus 10 including, withoutlimitation, raising and/or lowering of the person support apparatus 10.

Referring now to FIG. 2, an exploded view of the upper frame 102 andbase frame 101 of the person support apparatus 10 of FIG. 1 isschematically depicted. As depicted in FIG. 2, the person supportapparatus 10 also includes actuators 111, 113 (i.e., foot actuator 111and head actuator 113) which raise and/or lower the upper frame 102 withrespect to the base frame 101 when actuated by an electronic controlunit communicatively coupled to the actuators 111, 113, such as thecontrol box 24. In the embodiments described herein, the actuators 111,113 are linear actuators. However, it should be understood that otheractuators are contemplated and possible including, without limitation,pneumatic actuators, hydraulic actuators, rotary actuators (e.g.,motors), and the like.

In embodiments, person support apparatus 10 may include frame angularorientation sensor(s) for determining the angular orientation of theupper frame 102 with respect to the base frame 101. For example, inembodiments, orientation sensor(s) may include potentiometers (notshown) operatively associated with each of the foot actuator 111 and thehead actuator 113. The potentiometers are communicatively coupled to thecontrol box 24 of the person support apparatus 10, either by wires orwirelessly, and transmit signals to the control box 24 indicative of,for example, the stroke length of the foot actuator 111 and the headactuator 113 which, in turn, can be correlated to the angularorientation and height of the upper frame 102 with respect to the baseframe 101 such as in a look up table (LUT) stored in a memory of thecontrol box. For example, the LUT may contain an array of angularorientations (in degrees))(° of the upper frame 102 with respect to thebase frame 101 that are indexed according to the value of the signalsoutput by the potentiometers operatively associated with each of thefoot actuator 111 and the head actuator 113. Additionally, the LUT maycontain an array of distances indicating the spacing between the upperframe 102 and the base frame 101 indexed according to the value of thesignals output by the potentiometers operatively associated with each ofthe foot actuator 111 and the head actuator 113. In embodiments, thedistances may also be indexed according to the angle between the upperframe 102 and the base frame 101.

In embodiments, the upper frame 102 includes an end rail 71 proximatethe foot end 120 and an end rail 72 proximate the head end 122, and siderails 73, 74 disposed between and coupled to the end rail 71 and the endrail 72. The upper frame 102 includes cable tie locking mounts 81 andupper pivot projection features 90 that project from side rails 73, 74.Similarly, the base frame 101 includes an end rail 61 proximate the footend 120 and an end rail 62 proximate the head end 122, and sides rails63, 64 disposed between and coupled to the end rail 61 and the end rail62. In embodiments, the base frame 101 further includes one or moresensors for detecting and determining a load applied to the personsupport apparatus 10 such as, for example, the weight of a personpositioned on the person support apparatus 10. In embodiments, the oneor more sensors may include load beams (not shown) disposed within theside rails 63, 64 of the base frame 101. In other embodiments, the oneor more sensors may include load cells (not shown) disposed within theside rails 63, 64 of the base frame 101. The one or more sensors may becommunicatively coupled to a control box 24 of the person supportapparatus 10, either by wires or wirelessly, and transmit a signal tothe control box indicative of the weight of a person positioned on theperson support apparatus 10. The base frame 101 may also include anangular orientation sensor, such as an inclinometer I, attached to orintegrated in one of the side rails 63, 64. The inclinometer I may becommunicatively coupled to a control box 24 of the person supportapparatus 10, either by wires or wirelessly, and transmits a signal tothe control box 24 indicative of the angular orientation of the personsupport apparatus 10 with respect to horizontal level.

The base frame 101 further includes a linkage 3 (i.e., a foot linkage 3)pivotally coupled to the base frame 101 proximate the foot end 120. Thefoot linkage 3 is also pivotally coupled to the upper frame 102 andfacilitates raising and lowering the foot end 120 of the upper frame 102with respect to the base frame 101. Specifically, a first end 32 of thefoot linkage 3 is pivotally coupled to the base frame 101 between theside rails 63, 64. A second end 34 of the foot linkage 3 is pivotallycoupled to the upper frame 102 between side rails 73, 74. For example,the second end 34 is received within pivot projection features 90 (e.g.,half of a bearing) extending from each of the side rails 73, 74 and apivot strap 85 (e.g., half of a bearing) that is joined to each pivotprojection feature 90 via fasteners 86. In embodiments, the ends of thefoot linkage 3 may be disposed in bearing blocks 65 attached to the baseframe 101.

As shown in FIG. 2, the foot linkage 3 may further include a yoke 36coupling the foot actuator 111 to the foot linkage 3. The yoke 36 may bedisposed between ends 32, 34 of the foot linkage 3 and includes a pairof walls defining an actuator receiving space therebetween configured toreceive and be pivotally coupled to (through a fastener 88, for example)an end of the foot actuator 111.

The base frame 101 further includes a linkage 5 (i.e., a head linkage 5)pivotally coupled to the base frame 101 proximate the head end 122. Thehead linkage 5 is also pivotally coupled to the upper frame 102 andfacilitates raising and lowering the head end 122 of the upper frame 102with respect to the base frame 101. Specifically, a first end 52 of thehead linkage 5 is pivotally coupled to the base frame 101 between siderails 63, 64 proximate the head end 122 of the base frame 101. Inembodiments, the first end 52 of the head linkage 5 may be engaged withguide channels 66 attached to the side rails 63, 64 of the base frame101 such that a first end of the head linkage 5 is slidable with respectto the base frame 101. A second end 54 of the head linkage 5 ispivotally coupled to the upper frame 102 between side rails 73, 74proximate the head end 122 of the upper frame 102. In embodiments, thesecond end 54 of the head linkage 5 is received within pivot projectionfeatures 90 (e.g., half of a bearing) extending from each of the siderails 73, 74 and a pivot strap 85 (e.g., half of a bearing) that isjoined to each pivot projection feature 90 via fasteners 86.

As shown in FIG. 2, the head linkage 5 may further include a yoke 56coupling the head actuator 113 to the head linkage 5. The yoke 56 may bedisposed between ends 52, 54 of the head linkage 5 and may include apair of walls defining an actuator receiving space therebetweenconfigured to receive and be pivotally coupled to an end of the actuator113.

In the embodiments described herein, the head actuator 113 and the footactuator 111 may be, for example, pivotally mounted to the base frame101 to enable raising or lowering the upper frame 102 with respect tothe base frame 101. Alternatively, the head actuator 113 and the footactuator 111 may be pivotally mounted to the upper frame 102 to enableraising or lowering the upper frame 102 with respect to the base frame101. In yet another embodiment, at least one of the head actuator 113and the foot actuator 111 may be pivotally mounted to the upper frame102 and the other of the head actuator 113 and the foot actuator 111 maybe pivotally mounted to the base frame 101.

Still referring to FIG. 2, actuation of the head actuator 113 may thusresult in a hi-lo (or upper/lower movement) of the upper frame 102 withrespect to the base frame 101 at the head end 122, and actuation of thefoot actuator 111 may result in a hi-lo movement of the upper frame 102with respect to the base frame 101 at the foot end 120. That is,actuation of the foot actuator 111 causes the foot linkage 3 to pivotwith respect to the upper frame 102 and the base frame 101, therebyraising or lowering the foot end 120 of the upper frame 102 with respectto the base frame 101. Accordingly, it should be understood that thefoot actuator 111 facilitates raising and lowering the foot end 120 ofthe person support apparatus 10. Similarly, actuation of the headactuator 113 causes the head linkage 5 to pivot with respect to theupper frame 102 and the base frame 101, thereby raising or lowering thehead end 122 of the upper frame 102 with respect to the base frame 101.Accordingly, it should be understood that the head actuator 113facilitates raising and lowering the head end 122 of the person supportapparatus 10. Based on the foregoing, it should be understood that thefoot actuator 111 and the head actuator 113 may be utilized to adjustthe height of the upper frame 102 with respect to the base frame 101 andthe floor 500 (FIG. 1). It should also be understood that the footactuator 111 and the head actuator 113 may be operated independently orin conjunction with one another to adjust the angular orientation of theupper frame 102 (by controlling heights of ends 120, 122 with respect toone another and relative to horizontal, for example) with respect to thebase frame 101 and the floor 500.

As depicted in FIG. 2, the person support apparatus 10 further includesa torso support section 91 as part of the torso frame 109 (FIG. 1). Thetorso support section 91 is pivotally coupled to the upper frame 102proximate the head end 122 of the upper frame 102. In embodiments, thetorso support section 91 includes a deck 94 that is pivotally coupled tothe upper frame 102 with support brackets 92, 93 attached to the siderails 73, 74 of the upper frame 102. The deck 94 further comprises ayoke 96 coupled to an underside of the deck 94, such as to a framestructure (not shown) disposed on the underside of the deck 94. Thetorso support section 91 also includes a torso actuator 95 that ispivotally coupled to the deck 94 with the yoke 96 and affixed to aportion of the upper frame 102. The torso actuator 95 may also becommunicatively coupled to an electronic control unit, such as thecontrol box 24, which may be used to actuate the torso actuator 95.Actuation of the torso actuator 95 causes the deck 94 to pivot withrespect to the support brackets 92, 93 and the upper frame 102, therebychanging the angular orientation of the deck 94 with respect to theupper frame 102.

In embodiments, the torso support section 91 of the person supportapparatus 10 includes an orientation sensor (not shown) for determiningthe angular orientation of the deck 94 of the torso support section 91relative to the upper frame 102. In embodiments, the orientation sensormay be, for example, an inclinometer affixed to an underside of the deck94. The inclinometer may be communicatively coupled to a control box ofthe person support apparatus 10, either by wires or wirelessly, andtransmits a signal to the control box indicative of the angle ofinclination of the deck 94 with respect to the upper frame 102. In someother embodiments, the orientation sensor may include a potentiometer(not shown) operatively associated with the torso actuator 95. Thepotentiometer is communicatively coupled to a control box of the personsupport apparatus 10, either by wires or wirelessly, and transmits asignal to the control box indicative of, for example, the stroke lengthof the torso actuator 95 which, in turn, can be correlated to theangular orientation of the deck 94 with respect to the upper frame 102such as in a look up table (LUT) stored in a memory of the control box.

Referring now to FIGS. 1-3, the control box 24 of the person supportapparatus of FIG. 1 is schematically depicted. In embodiments, thecontrol box 24 includes a processor and a non-transitory computerstorage medium storing computer readable and executable instructionswhich, when executed by the processor, control the functions of theperson support apparatus 10. In embodiments, the control box 24 furtherincludes a graphical user interface (GUI) as depicted in FIG. 3. The GUIassociated with the control box 24 may be a Graphical CaregiverInterface (“GCI®”) commercially available from Hill-Rom Services, Inc.of Batesville, Ind., for example. A user, such as a caregiver, may beable to adjust the angular orientation of the upper frame 102 of theperson support apparatus 10 and move the upper frame 102 in upwards anddownwards directions (indicated by arrow 600) relative to the base frame101 via a soft key or button provided on the GUI of control box 24. TheGUI of the control box 24 may include, for example, a home screenindicator 24A, one or more temperature status indicators 24B of asurface of the bladder portion, a home menu control option 24C, analerts menu control option 24D, and a scale menu control option 24E toweigh a person supported on the person support apparatus 10, forexample. The GUI of the control box 24 may further include a bed therapymenu control option 24F, a reminder menu control option 24G, apreferences menu control option 24H, a down (and up) arrow menu controloption 24I, and a help control option 24J. Further, the GUI of thecontrol box 24 may graphically provide a head angle alert statusindicator 24K, a head angle orientation indicator 24L showing an angleof the torso frame 109 with respect to the upper frame 102 (shown as 58°in the example of FIG. 3), a bed height status indicator 24M, and ascreen lock control option 24N. The GUI of the control box 24 mayfurther include an air fluidization status indicator 24P, a scale zerostatus indicator 24Q, a bed exit alert status indicator 24R, and analternative preemptive bed exit alert silence control option 24O. Othercontrol features and options accessible to a caregiver via the GUI ofthe control box 24 to control and/or collect data with respect to theperson support apparatus 10 are contemplated and are within the scope ofthis disclosure.

Other types of control panels, pendants, and/or control units forcontrolling the person support apparatus 10 are also contemplated. Forexample, FIG. 4 schematically depicts the angle and height control panel26 of the person support apparatus of FIG. 1, and FIG. 5 schematicallydepicts the pendant 28 of the person support apparatus of FIG. 1. Thecontrol panel 26 may be, for example, communicatively coupled to theprocessor and non-transitory computer storage medium of the control box24 to facilitate the operation of various functions of the personsupport apparatus 10. The control panel 26 of FIG. 4 may include a bedtherapy (air fluidization) control and indicator option 26A, head up anddown controls 26B with a lockout indicator, a head angle display 26C(shown as 30° in the example of FIG. 4), and bed up and down controls26D with a lockout indicator. The bed up and down controls 26D may beused to raise or lower the upper frame 102 via the foot and headactuators 111, 113, as described above. The control panel 26 may furtherinclude a surface transfer control 26E, a side transfer control 26F, anda service required indicator 26G. Additionally, the control panel 26 mayinclude a lockout control option 26H and a bed not down indicator 26I(indicating an elevated or raised upper frame 102, for example).

The pendant 28 depicted in FIG. 5 may be, for example, communicativelycoupled to the processor and non-transitory computer storage medium ofthe control box 24 to facilitate the operation of various functions ofthe person support apparatus 10. The pendant 28 may include head up anddown controls 28A to control the angle of the torso frame 109 withrespect to the upper frame 102, a comfort adjust zone select control 28Bincluding indicators aligned with certain portions of a resting person,and comfort adjust pressure increase and decrease controls 28C andassociated indicators which may be used, for example, to adjust thepressure in the fluid bladders 131 located in the upper portion 130 ofthe mattress system 104.

Referring now to FIG. 6, another embodiment of a person supportapparatus 100 is schematically depicted. The person support apparatus100 of this embodiment, for example, may be similar to the personsupport apparatus 10 of FIGS. 1 and 2. It should be understood thatother person support apparatuses compatible with the methods describedherein are contemplated and possible. In this embodiment, the personsupport apparatus 100 includes actuators 111, 113 similar to actuators111, 113 of the person support apparatus 10 of FIGS. 1 and 2 and thatallow for an upward or downward movement along arrows 600A, 600Brespectively. The person support apparatus 100 further includes aninclinometer I.

The person support apparatus 100 in this embodiment generally includes abase frame 101 and an upper frame 102 on which a mattress system 104 issupported. The base frame 101 supports the person support apparatus 100on the floor 500 and may include wheels 106 (such as casters) tofacilitate relocating and/or repositioning the person support apparatus100 on the floor 500. The upper frame 102 is coupled to the base frame101 with pivoting linkages 103, 105 which facilitate raising andlowering the upper frame 102 with respect to the base frame 101, asindicated by arrow 600. More particularly, a first end of a foot linkage103 is pivotally coupled to the base frame 101 and a second end of thefoot linkage 103 is pivotally coupled to the upper frame 102. Similarly,a first end of a head linkage 105 is pivotally coupled to the base frame101 and a second end of the head linkage 105 is pivotally coupled to theupper frame 102.

In addition, the person support apparatus 100 also includes actuators111, 113 which, when actuated by an electronic control unit (not shown)communicatively coupled to the actuators 111, 113, raise and/or lowerthe upper frame 102 with respect to the base frame 101. In theembodiments described herein, the actuators 111, 113 are linearactuators. However, it should be understood that other actuators arecontemplated including, without limitation, pneumatic actuators,hydraulic actuators, rotary actuators (e.g., motors), and the like.Actuation of the foot actuator 111 causes the foot linkage 103 to pivotwith respect to the upper frame 102 and the base frame 101, therebyraising or lowering the foot end 120 of the upper frame 102 with respectto the base frame 101. Accordingly, it should be understood that thefoot actuator 111 facilitates raising and lowering the foot end 120 ofthe person support apparatus 100. Actuation of the head actuator 113causes the head linkage 105 to pivot with respect to the upper frame 102and the base frame 101, thereby raising or lowering the head end 122 ofthe upper frame 102 with respect to the base frame 101. Accordingly, itshould be understood that the head actuator 113 facilitates raising andlowering the head end 122 of the person support apparatus 100. Based onthe foregoing, it should be understood that the foot actuator 111 andthe head actuator 113 may be utilized to adjust the height of the upperframe 102 with respect to the base frame 101 and the floor 500. Itshould also be understood that the foot actuator 111 and the headactuator 113 may be used to adjust the angular orientation of the upperframe 102 with respect to the base frame 101 and the floor 500 about anaxis of rotation which is generally parallel to the y axis of thecoordinate axes depicted in FIG. 6. That is, the foot actuator 111 andthe head actuator 113 may be operated independently or in conjunctionwith one another to adjust the angular orientation of the upper frame102 with respect to the base frame 101 and the floor 500.

In embodiments, person support apparatus 100 may include frame angularorientation sensor(s) for determining the angular orientation of theupper frame 102 with respect to the base frame 101. For example, inembodiments, orientation sensor(s) may include potentiometers (notshown) operatively associated with each of the foot actuator 111 and thehead actuator 113. The potentiometers are communicatively coupled to thecontrol box 24 of the person support apparatus 100, either by wires orwirelessly, and transmit signals to the control box 24 indicative of,for example, the stroke length of the foot actuator 111 and the headactuator 113, which, in turn, can be correlated to the angularorientation and height of the upper frame 102 with respect to the baseframe 101 such as in a look up table (LUT) stored in a memory of thecontrol box 24. For example, the LUT may contain an array of angularorientations (in degrees (°) of the upper frame 102 with respect to thebase frame 101 that are indexed according to the value of the signalsoutput by the potentiometers operatively associated with each of thefoot actuator 111 and the head actuator 113. Additionally, the LUT maycontain an array of distances indicating the spacing between the upperframe 102 and the base frame 101 indexed according to the value of thesignals output by the potentiometers operatively associated with each ofthe foot actuator 111 and the head actuator 113. In embodiments, thedistances may also be indexed according to the angle between the upperframe 102 and the base frame 101.

Still referring to FIG. 6, in embodiments, the person support apparatus100 may include a torso frame 109 which is pivotally coupled to theupper frame 102. The torso frame 109 may be pivoted with respect to theupper frame 102 thereby facilitating increasing an angle of inclinationof the mattress system 104 proximate the head end 122 of the personsupport apparatus 100. In embodiments, an actuator (not shown) may becoupled to the upper frame 102 and the torso frame 109 to facilitatepivoting the torso frame 109 with respect to the upper frame 102 via anelectronic control unit.

The mattress system 104 includes an upper portion 130 and a lowerportion 140. The upper portion 130 of the mattress system 104 ispositioned on the torso frame 109. In some embodiments, the upperportion 130 of the mattress system 104 may generally include one or morefluid bladders 131 which may be inflated or deflated to adjust theposition of a person on the mattress system 104 and/or increase ordecrease the firmness of a portion of the mattress system 104 accordingto the person's preference.

Referring now to FIGS. 6 and 7A, the lower portion 140 of the mattresssystem 104 includes a fluidized bed of particulate material as describedherein with respect to the embodiment of the person support apparatus 10depicted in FIGS. 1 and 2. Specifically, the lower portion 140 of themattress system 104 includes a bladder portion 110 enclosed by sidewalls141 a, 141 b, 141 c, 141 d which generally form a tub portion 115 of themattress system 104. The sidewalls 141 a, 141 b, 141 c, 141 d may beformed from foam (such as, for example, open and/or closed cellpolyurethane foam), fluid bladders, or a composite of foam and fluidbladders. The bladder portion 110 contains particulate material, such asglass, plastic, and/or ceramic microspheres (i.e., beads). Afluidization system (not shown), such as a pump, may be used to pump afluid, such as gas or air, into the interior volume of the bladderportion 110, thereby fluidizing the particulate material and creating acentral, fluidized bed (of fluidized particulate material) 112 in thelower portion 140 of the mattress system 104. This fluidized bed 112assists in distributing and redistributing pressure against the skin ofa person positioned on the mattress system 104. It should be understoodthat the lower portion 140 of the mattress system 104 of the personsupport apparatus 10 depicted in FIG. 1 has the same general structureas the lower portion 140 of the mattress system 104 of the personsupport apparatus 100 depicted in FIGS. 6 and 7A.

Reference will now be made to the embodiment of the person supportapparatus 10 depicted in FIGS. 1-2, the embodiment of the person supportapparatus 100 depicted in FIG. 6, and the mattress system 104 depictedin FIGS. 7A-7D to describe embodiments of methods of operating therespective person support apparatuses 10, 100.

Referring now to FIGS. 1-2, 6, and 7A-7D, the fluidization of theparticulate material to create the fluidized bed 112 causes theparticulate material within the bladder portion 110 to be mobile andreadily redistributed throughout the bladder portion 110. That is, whenthe upper frame 102 is level with respect to horizontal (i.e., gravity),the particulate material will have a uniform depth D within the bladderportion 110, as depicted in FIG. 7B. However, when the upper frame 102is at an angle with respect to horizontal, the particulate material willmigrate to one end of the bladder portion 110 due to gravity. Forexample, FIG. 7C schematically depicts a cross section of the bladderportion 110 when the head end of the upper frame 102 is tilted downwardby 1°. This tilt causes the particulate material to migrate within thebladder portion 110 towards the head end of the bladder portion 110,thereby increasing the depth DH of the particulate material at the headend of the bladder portion 110, and decreasing the depth DF of theparticulate material at the foot end of the bladder portion 110. By wayof contrast, FIG. 7D schematically depicts a cross section of thebladder portion 110 when the foot end of the upper frame is tilteddownward by 0.5°. This tilt causes the particulate material to migratewithin the bladder portion 110 towards the foot end of the bladderportion 110, thereby increasing the depth DF of the particulate materialat the foot end of the bladder portion 110, and decreasing the depth DHof the particulate material at the head end of the bladder portion 110.

In order to prevent a person positioned on the mattress system 104 from“bottoming” in the bladder portion 110 (that is, in order to maintain anadequate volume of particulate material between the person and thesupport frame), it has been determined that the foot end of the upperframe 102 should be elevated with respect to the head end of the upperframe 102. This causes the depth DH of the particulate material in thehead end of the bladder portion 110 to be greater than the depth DF ofthe particulate material in the foot end of the bladder portion 110 andalso decreases or mitigates the migration of particulate material fromthe head to the foot end. More specifically, it has been determined thata person will generally be positioned on the mattress system 104 suchthat their sacrum (i.e., lower back/gluteus muscles) is positioned onthe bladder portion proximate the head end of the bladder portion 110,as indicated by line 700, which corresponds to a maximum immersion depthlocation of the person. As such, the greatest percentage of the person'sweight is incident on the bladder portion 110 along this line,potentially causing the displacement of beads towards the foot end ofthe bladder portion 110 and potentially leading to the person bottomingin the fluidized bed 112. However, if the foot end of the bladderportion 110 is raised with respect to the head end of the bladderportion 110, the depth of beads is greater along the line 700,decreasing the potential for bottoming out in the fluidized bed 112. Inthe embodiments described herein, with respect to the referenceposition, the foot end of the upper frame 102 is inclined at an anglegreater than 0° and less than 1°, such as less than or equal to 0.75°,less than or equal to 0.5°, or even less than or equal to 0.25°, inorder to achieve and maintain an appropriate distribution of particulatematerial in the bladder portion 110. The reference position may be in arange from about +0.1° to about −0.5° such that the person supportapparatus 10, 100 is oriented with the foot end 120 of the personsupport apparatus 10, 100 when the reference position is in a negativeend of the range, such as at −0.5°. In embodiments described herein,with respect to the reference position, the foot end of the upper frame102 is disposed higher than the head end and is inclined at an anglethat is in a range of from about 0° to about 10.1°.

In addition, when moving the upper frame 102 either up or down relativeto the base frame 101 changes in the relative inclination/declination ofthe head end 122 and the foot end 120 of the upper frame 102 can resultin a significant and often undesirable redistribution of the particulatematerial within the bladder portion. More specifically, it has beenfound that the angular orientation of the upper frame should bemaintained within (i.e., in a range from about) +/−0.5°, such as+/−0.4°, +/−0.3°, +/−0.25° (i.e., within an orientation referencerange), relative to or of a predetermined, nominal reference orientation(i.e., the reference position), such as an orientation where the footend 120 of the upper frame 102 is elevated above the head end 122 of theupper frame 102, to avoid significant redistribution of the particulatematerial in the bladder portion 110. Embodiments of the methods andcontrol systems described herein allow the relative orientation of theupper frame 102 to be maintained within a range of +/−0.5° of apredetermined, nominal reference orientation as the upper frame 102 israised and/or lowered relative to the base frame 101.

Still referring to FIGS. 1-2 and 6, in embodiments, the person supportapparatus 10, 100 is maintained within a range of +/−0.5° of thepredetermined, nominal reference orientation as the upper frame 102 israised and/or lowered relative to the base frame 101 using aproportional-integral-derivative (PID) algorithm. This method utilizesan angle derived from a potentiometer operatively associated with one ofthe actuators (i.e., the foot actuator 111 or the head actuator 113) asan input during hi-lo motion and adjusts the speed of one of theactuators relative to the other to maintain the angle of orientation ofthe upper frame 102 at the nominal reference orientation. The angularorientation of the upper frame as determined/derived from thepotentiometer operatively associated with one of the actuators is morestable and, hence, more accurate than the angular orientation derivedfrom an inclinometer device. However, the inclinometer device may beused to determine an angle of the floor relative to horizontal and,thereafter, this value may be used to correct any errors in thepotentiometer-based angle prior to the start of movement of the upperframe 102.

In embodiments, the actuators have an initial soft start during whichthe actuator that is driven at a greater speed to correct for anystarting error starts 200 ms before the other actuator. If thedifference in the angle between the head and foot ends of the uppersupport frame is zero, one actuator is still started after the otherusing the 200 ms delay. During this delay, the actuator in motion isincremented at a 10% duty cycle speed. After the delay has expired, theactuator requiring higher speed is incremented at a 10% duty cycle andthe slower actuator increments at a 5% duty cycle. In embodiments, thefirst actuator is incremented at a first duty cycle speed that is atleast double a second duty cycle speed at which the second actuator isincremented, and the first duty cycle speed may be at a 10%pulse-width-modulation and the second duty cycle speed at 5%pulse-width-modulation.

In embodiments, after the actuators are started using the aforementioned“soft start”, the PID algorithm is implemented using the potentiometerderived angle, after correcting for any inclinometer angular value readprior to the starting drive motion. Moving the upper frame in thismanner maintains the bed at the nominal reference orientation thuspreventing excessive migration of the support beads from under theperson. In addition, using a potentiometer-based angle during movementof the upper frame 102 avoids response delays due to filtering ofsignals from an inclinometer.

Referring now to FIGS. 1-2 and 6-8, in embodiments, the control box 24of the person support apparatus 10, 100 is communicatively coupled tothe first and second potentiometers P1 and P2 operatively associatedwith the head and foot actuators, and the inclinometer I. As notedhereinabove, the first potentiometer P1 may be operatively associatedwith the head actuator 113 at a head end 122 (e.g., a first or secondend) of the person support apparatus 10, 100 and may output a firstreading indicative of an angular orientation of the head end 122 of theupper frame 102 relative to the base frame 101. For example, anglesstored in a lookup table of a storage database of the control box 24 maybe indexed as a function of the potential measured by the potentiometer,as described herein. The second potentiometer P2 may be operativelyassociated with the foot actuator 111 at a foot end 120 (e.g., a secondor first end) of the person support apparatus 10, 100 and may output asecond reading indicative of an angular orientation of the foot end 120of the upper frame 102 relative to the base frame 101. For example,angles stored in a lookup table of a storage database of the control boxmay be indexed as a function of the signal output by the potentiometer,as described herein. The inclinometer I may output a floor angle readingof the person support apparatus 10, 100 relative to horizontal level. Asdescribed herein, the control box 24 may include a graphical userinterface (GUI) to assist with adjusting the angular orientation of theupper frame 102 of the person support apparatus 10, 100 and moving theupper frame 102 of the person support apparatus 10, 100 in upwards anddownwards directions (indicated by arrow 600). The caregiver may be ableto adjust angular orientations of the upper frame 102 of the personsupport apparatus 10, 100 and move the upper frame 102 in upwards anddownwards directions (indicated by arrow 600) via a soft key or buttonprovided on the GUI of control box 24.

In embodiments, and referring to FIG. 8, the actuators 111, 113,associated potentiometers P1, P2 and/or inclinometer I arecommunicatively coupled to the control box 24 and the various componentsof upper frame 102 work in conjunction with one another to controlangular orientations of the upper frame 102 of the person supportapparatus 10, 100, as described in more detail below.

As shown in FIG. 8, in some embodiments the person support apparatus 10,100 includes a system 200 for controlling an angular orientation of theupper frame 102 of the person support apparatus 10, 100. The system 200includes the control box 24, the inclinometer I, the potentiometers P1and P2, and the actuators 111, 113. The system 200 further includesfirst and second PID controllers, PID1 and PID2, and a microcontroller204 to which the system components are communicatively coupled viacommunication paths 206 and 208A-208B, as described further below,either by wires or wirelessly. The microcontroller 204, such as anelectronic control unit, has a processor and a non-transitory storagemedium, such as a memory, containing readable and executableinstructions which, when executed by the processor, cause the processorto enact steps. Such steps, for example, may result in instructing theelectronic control unit to adjust at least one of the height and angularorientation of the upper frame 102 of the person support apparatus 10,100 such that the fluidized particulate material has a predetermineddistribution in the bladder portion 110 during such movements and upondiscontinuing such movements. The microcontroller 204 is alsocommunicatively coupled to the GUI of the control box 24. Themicrocontroller 204 and the GUI are able to exchange electrical signalstherebetween to facilitate operation of actuators 111, 113 to controlthe angular orientation of the upper frame 102 of the person supportapparatus 10, 100 with respect to the base frame 101 and to facilitateupwards and downwards (i.e., high and low or “hilo” or “hi-lo”) movementof the upper frame 102 of the person support apparatus 10, 100.

In embodiments, the system 200 receives an input from a GUI of controlbox 24 to instruct the microcontroller 204 of a desired upwards ordownwards movement of the upper frame 102 of the person supportapparatus 10, 100 (e.g., when an operator desires to raise or lower theheight of the person support apparatus 10, 100 and, in particular, theupper frame 102 of the person support apparatus 10, 100). The system 200operates to ensure the bladder portion 110 is in an orientation suchthat the fluidized particulate material within the bladder portion 110has a predetermined distribution and will remain so with any upwards ordownwards movement of the upper frame 102 of the person supportapparatus 10, 100. For example, and as discussed above, thepredetermined distribution of the particulate material may be such thatthe foot end of the bladder portion 110 is slightly elevated withrespect to the head end of the bladder portion 110 such that a depth ofthe fluidized particulate material at the head end is greater than atthe foot end, particularly at the point of maximum immersion. Alongcommunication path 206, the microcontroller 204 receives a reading fromthe inclinometer I indicative of a floor angle of the person supportapparatus 10, 100 relative to horizontal. And along communication paths208A and 208B, the microcontroller 204 receives first and secondreadings from potentiometers P1 and P2 associated with actuators 113,111, for example, that are indicative of respective angular orientationsof respective head and foot ends 122 and 120 of the upper frame 102 ofthe person support apparatus 10, 100. For example, a stroke length ofthe actuator 111, 113 dictates the angular orientation of the upperframe 102 of the person support apparatus 10, 100 with respect tohorizontal. The amount of the stroke length is associated with theamount of angular rotation of the upper frame 102 of the person supportapparatus 10, 100 about an axis parallel to the y axis of FIG. 6. Theangular orientation of the upper frame 102 of the person supportapparatus 10, 100 may also be adjusted to be maintained within anacceptable reference range with respect to the base frame 101 of theperson support apparatus 10, 100.

The readings from the potentiometers P1 and P2 are indicative ofinternal reference angles of the upper frame 102 relative to the baseframe 101. As such, the readings from potentiometers P1 and P2 may becorrected to account for non-horizontal floor angles FA1, FA2 relativeto horizontal as determined by the inclinometer I. In embodiments, thefloor angle may be a single floor angle read from a single inclinometer,for example. The readings from potentiometers P1 and P2 are calibratedand corrected to account for floor angle by adjusting the internalreference angles based on the actual floor angles to obtain correctedpotentiometer readings AA1, AA2, as described further below in greaterdetail with respect to FIG. 9. These corrected potentiometer readingsAA1, AA2 are respectively input into first and second PID controllersPID1, PID2. The outputs of first and second PID controllers PID1, PID2are used to adjust the operation of the actuators, such as a speed ofoperation and/or stroke length of the actuators, so that the upper frame102 has a specified orientation with respect to the base frame 101 andthe fluidized particulate material has a predetermined distributionwithin the bladder portion 110. In embodiments, the outputs of first andsecond PID controllers PID1, PID2 may be sent through a control feedbackloop to continue adjusting input potentiometer readings P1 and P2 untilthe outputs of first and second PID controllers PID1, PID2 are within anominal reference orientation, within which the fluidized particulatematerial contained the bladder portion 110 of the person supportapparatus 10, 100 has a predetermined distribution.

In embodiments, a method for controlling an angular orientation of aperson support apparatus 10, 100 including a support surface (e.g., themattress system 104) having a bladder portion 110 containing fluidizedparticulate material (e.g., the fluidized bed 112 of particulatematerial), an upper frame 102, and a base frame 101 may includeadjusting a height of the upper frame 102 with respect to the base frame101 with at least one of a first actuator and a second actuator atrespective first and second actuator speeds. In the embodimentsdescribed herein, the first actuator may be one of actuators 111, 113and the second actuator may be the other of actuators 111, 113. Themethod may include determining a dynamic angular orientation of theupper frame 102 with respect to the base frame 101 based on at least oneof an operating characteristic of the first actuator and an operatingcharacteristic of the second actuator, and determining a correctedangular orientation based on the dynamic angular orientation and a floorangle indicative of the orientation of the base frame with respect tohorizontal (the operating characteristic may be, for example, a strokelength of the respective actuator). The method may further includecomparing the corrected angular orientation with an orientationreference range, and adjusting at least one of the first actuator speedand the second actuator speed when the corrected angular orientation isoutside the orientation reference range until the corrected angularorientation is within the orientation reference range. In embodiments,the method may further include an initial step of determining the floorangle indicative of the orientation of the base frame with respect tohorizontal based on a value generated from an inclinometer I disposed onthe person support apparatus 10, 100. In embodiments, at least one ofthe first actuator speed and the second actuator speed are adjusted andthe dynamic angular orientation is determined as the upper frame 102transitions with respect to the base frame 101 from a first height to asecond height. The dynamic angular orientation is determined at leastpartially based on one or more values generated from at least one of afirst potentiometer associated with the first actuator and a secondpotentiometer associated with the second actuator. In the embodimentsdescribed herein, the first potentiometer may be one of potentiometersP1, P2 and the second potentiometer may be the other of potentiometersP1, P2. The orientation reference range may be measured relative to areference position of the person support apparatus, which may be at0.25° such that the person support apparatus is oriented with a foot endof the person support apparatus higher than a head end. The referenceposition may be in a range from about +0.1° to about −0.5° such that theperson support apparatus is oriented with a foot end of the personsupport apparatus higher than a head end when the reference position isin a negative end of the range. The orientation reference range may inone of the following ranges relative to the reference position: a rangefrom about −0.4° to about +0.4° relative to the reference position, anda range from about −0.25° to about +0.25° relative to the referenceposition.

In embodiments, a method for controlling an angular orientation of aperson support apparatus 10, 100 that includes a support surface (e.g.,the mattress system 104) having a bladder portion 110 containingfluidized particulate material (e.g., the fluidized bed 112 ofparticulate material) may include actuating at least one of a firstactuator and a second actuator, respectively coupled to the personsupport apparatus at a first end and a second end, at a respective firstactuator speed and a second actuator speed to raise or lower a height ofthe person support apparatus 10, 100. In the embodiments describedherein, the first end may be one of the ends 120, 122 and the second endmay be the other of the ends 120, 122. The method may further includereceiving a first reading indicative of a first angular orientation ofthe first end of the person support apparatus 10, 100 with respect tothe second end and relative to horizontal. The first reading may be atleast generated from a first sensor and a second sensor respectivelyassociated with the first actuator and the second actuator. The firstsensor and/or the second sensor may be any of the sensors as describedherein such as a potentiometer and/or inclinometer or another suitablesensor. The method may further include determining a corrected firstreading indicative of the first angular orientation based on the firstreading and a calibration of the person support apparatus 10, 100,comparing the corrected first reading and an orientation referencerange, and actuating at least one of the first actuator and the secondactuator automatically at a different speed when the corrected firstreading is outside the orientation reference range until an adjustedcorrected first reading indicative of an adjusted first angularorientation is within the orientation reference range. In embodiments,the method may further include comprising calibrating the person supportapparatus 10, 100 to generate the calibration, which includescalculating, automatically with an inclinometer I, a floor angleassociated with the person support apparatus 10, 100 relative tohorizontal.

In embodiments, the first reading may be generated from at least one ofa first potentiometer associated with the first actuator and a secondpotentiometer associated with the second actuator, and determining thecorrected first reading may include calculating the corrected firstreading based on the first reading and the floor angle. Further, themethod may include receiving input from at least one of the firstpotentiometer and the second potentiometer respectively in at least oneof a first PID controller and a second PID controller, outputting atleast one of a first actuator drive signal from the first PID controllerand a second actuator drive signal from the second PID controller, andrepeating the receiving and outputting steps until the adjustedcorrected first reading indicative of the adjusted first angularorientation is within the orientation reference range.

In embodiments, the first reading may be at least partially generatedfrom a first potentiometer associated with the first actuator and asecond potentiometer associated with the second actuator, and actuatingat least one of the first actuator and the second actuator comprisesoutputting a stroke length signal related to a stroke length for therespective first and second actuators, wherein the stroke length of thefirst actuator is an input with respect to the first potentiometer andthe stroke length of the second actuator is an input with respect to thesecond potentiometer. The method may further include receiving therespective stroke lengths for the first and second actuators associatedwith the corrected first reading as a respective input in at least oneof a first PID controller and a second PID controller, outputting atleast one of a first actuator drive signal from the first PID controllerand a second actuator drive signal from the second PID controller, andrepeating the receiving and outputting steps until the adjustedcorrected first reading indicative of the adjusted first angularorientation is within the orientation reference range.

In embodiments, a system (e.g., system 200) for controlling an angularorientation of a person support apparatus 10, 100 may include at least afirst actuator associated with a head end as a first end and a secondactuator associated with a foot end as a second end of the personsupport apparatus, and an electronic control unit comprising a processorcommunicatively coupled to a non-transitory computer storage medium. Thenon-transitory computer storage medium stores instructions that may,when executed by the processor, cause the processor to perform the stepsset forth above and/or any steps as set forth herein.

Referring to FIGS. 1-9, for example, an exemplary method 300 of usingthe system 200 is described for controlling the angular orientation ofthe person support apparatus 10, 100 to maintain the fluidizedparticulate material contained within the bladder portion 110 of theperson support apparatus 10, 100 in a predetermined distribution withinthe bladder portion 110 when at least one of an angular orientation ofan end 120, 122 of the upper frame 102 of the person support apparatus10, 100 is adjusted or the person support apparatus is adjusted in anupwards or downwards direction (i.e., when adjusting a height of theupper frame 102 with respect to the base frame 101 with at least one ofa first actuator and a second actuator, which may respectively be eitherof actuators 111, 113 at respective first and second actuator speeds).Thus, in embodiments, actuating at least one of actuators 111, 113,which are respectively coupled to the person support apparatus at thefoot end 120 and the head end 122 of the person support apparatus 10,100, at respective speeds raises or lowers a height of the personsupport apparatus 10, 100.

In embodiments, the method 300 may include an initial step ofdetermining the floor angle indicative of the orientation of the baseframe 101 with respect to horizontal based on a value generated from aninclinometer I disposed on the person support apparatus 10, 100. In step302, for example, a reference angle is received based on an inclinometerreading from an inclinometer I of the person support apparatus 10, 100,which reading is indicative of a floor angle of the person supportapparatus 10, 100 relative to horizontal such that the floor angle isdetermined. In step 304, a reading from a first and/or secondpotentiometer P1, P2 is received automatically by the electronic controlunit, which reading (i.e., a first reading) is indicative of an angle(i.e., a first angular orientation of a first end with respect to asecond end, which may be either of ends 120, 122, and relative tohorizontal) or dynamic angular orientation of the upper frame 102 withrespect to the base frame 101 of the person support apparatus 10, 100.The readings generated from first and/or second potentiometers P1, P2 asfirst and/or second sensors (each associated with first and/or secondactuators that may be either of actuators 111, 113) may be based onrespective internal reference angles (i.e., values generated from thefirst and/or second potentiometers P1, P2) that do not account for floorangle, for example. To account for such floor angle (i.e., to determinea corrected first reading), the readings are calibrated using thereading from the inclinometer I to account for floor angle (i.e., thecorrected first reading is based on the first reading from thepotentiometers P1 and/or P2 and a calibration of the person supportapparatus 10, 100 to determine floor angle). For example, inembodiments, the method 300 includes calibrating the person supportapparatus 10, 100 to generate the calibration, which includescalculating (automatically with the inclinometer I) a floor angleassociated with the person support apparatus relative to horizontal.Thus, determining the corrected first reading may include calculatingthe first reading (i.e., generated from potentiometers P1 and/or P2) andthe floor angle (i.e., generated from the inclinometer I).

For example, in step 306, a corrected potentiometer reading or angle, orcorrected first and second readings, is determined (i.e., as a correctedangular orientation) automatically with the electronic control unitbased on the respective first and second readings from step 304 (i.e.,that determine the dynamic angular orientation) and a calibration of theperson support apparatus 10, 100 (i.e., that is based on a determinedfloor angle). The corrected first and second readings determined by theelectronic control unit may be based on readings from instruments suchas the potentiometers and other similar electronic instruments, whichare within the scope of this disclosure. The calibration may include,for example, calculating automatically with the inclinometer I a floorangle associated with the person support apparatus 10, 100 relative tohorizontal, and calculating automatically with the electronic controlunit the corrected first and second readings based on respectivereceived first and second readings from the potentiometers and the floorangle. For example, referring again to FIG. 8, the readings frompotentiometers P1 and P2 are calibrated and corrected to account forfloor angle by adjusting the internal reference angles based on theactual floor angles to obtain corrected potentiometer readings AA1, AA2.To do this, offset floor angles FA1, FA2 are calculated, which is arespective difference between inclinometer I and readings frompotentiometers P1, P2. Then, a sum of the readings from potentiometersP1, P2 and the offset floor angles FA1, FA2 provide correctedpotentiometer readings AA1, AA2, which reflect a reading frominclinometer I. In embodiments, input from the potentiometers P1 and/orP2 (indicative of respective stroke lengths of associated actuators 111,113) may be received in the first and/or second PID controllers PID1,PID2, and the controllers may each output an actuator drive signal foreach of actuators 111, 113 (i.e., as first and/or second actuator drivesignals), and may repeat these steps until an adjusted corrected firstreading indicative of the adjusted first angular orientation is withinthe orientation reference range as described herein. Further, actuatingthe actuators 111 and/or 113 may include outputting a stroke lengthsignal related to a respective actuator stroke length. A stroke lengthof each actuator 111, 113 (either which may be first and secondactuators) is an input to associated first and second potentiometers(i.e., either of potentiometers P1, P2).

Referring again to FIGS. 1-9 and step 308, in embodiments, theelectronic control unit may automatically compare corrected first and/orsecond readings (i.e., the corrected angular orientation) with anorientation reference range. When the first and/or second readings arewithin the orientation reference range (such as a coarse orientationreference range), the fluidized particulate material contained withinthe bladder portion 110 of the person support apparatus 10, 100 has adesired distribution within the bladder portion 110. In embodiments, ifthe corrected potentiometer angle is within the coarse orientationreference range in step 308, the method 300 continues to step 310 tocontinue using the respective first and/or second actuators 113, 111 tomove the upper frame 102 of the person support apparatus 10, 100 in anupwards or downwards direction (indicated by arrow 600) until a stopsignal is received by the electronic control unit. The orientationreference range may be, for example, the nominal reference orientationplus or minus (+/−) an angular tolerance as described above. Theorientation reference range may be, for example, within a range of fromabout −0.4° relative to the nominal reference orientation to about +0.4°relative to the nominal reference orientation, or within a range of fromabout −0.25° relative to the nominal reference orientation to about+0.25° relative to the nominal reference orientation. In embodiments,the orientation reference range may be, for example, a coarseorientation reference range that is within a range of from about −0.4°relative to the nominal reference orientation to about +0.4° relative tothe nominal reference orientation. A fine orientation reference rangemay be within the coarse orientation reference range and a breadth ofthe fine orientation reference range may be less than a breadth of thecoarse orientation reference range. The fine orientation reference rangemay be, for example, within a range of from about −0.25° relative to thenominal reference orientation to about +0.25° relative to the nominalreference orientation. It is contemplated that a single orientationreference range, rather than a coarse and a fine orientation referencerange, may be utilized to determine whether a corrected first reading iswithin or outside of the orientation reference range. Thus, wherever“coarse” or “fine” is described herein, a single orientation referencerange may be contemplated as well.

If the corrected potentiometer angle is outside the coarse orientationreference range in step 308, the method 300 continues on to step 312 toinput the corrected potentiometer angle into a PID controller. Inembodiments, when the corrected first and/or second readings (i.e., thecorrected angular orientation) are outside the orientation referencerange (e.g., outside the coarse orientation reference range), theelectronic control unit automatically adjusts the corrected first and/orsecond readings (i.e., through actuating respectively associated firstand/or second actuator speeds of actuators 111, 113 at a differentspeed) to obtain respective adjusted first and/or second readings (i.e.,an adjusted corrected first reading) indicative of respective adjustedfirst and/or second angular orientations of respective first and/orsecond ends 122, 120 of the person support apparatus 10, 100 (i.e.,indicative of an adjusted first angular orientation or corrected angularorientation) until the corrected angular orientation is within theorientation reference range. In embodiments, in step 312, the correctedpotentiometer reading or angle (that may be at least one of the firstand/or second readings described herein that generate, for example, thecorrected angular orientation) is input into an associated PIDcontroller PID1, PID2. For example, the corrected potentiometer readingsAA1, AA2 are input into respective PID controllers PID1, PID2. Inembodiments, to obtain adjusted first and/or second readings, in step314, a PID controller value is output to determine a respective actuatordrive signal that, in step 316, is applied to drive a respective footand/or head actuator 111, 113 (e.g., either of which may be a firstactuator or a second actuator). In embodiments, the actuator drivesignals applied to drive the respective actuators 111, 113 may relate toa stroke length of the actuator and/or a speed of actuation of theactuator (i.e., an operating characteristic of the actuators 111, 113).In embodiments, the foot actuator 111 and/or the head actuator 113 haverespective speeds that are adjusted as the upper frame 102 transitionswith respect to the base frame 101 from a first height to a secondheight during which time the dynamic angular orientation is determined.For example, in the case of linear actuators, increasing or decreasing astroke length of the actuator adjusts the angular orientation (i.e., thedynamic angular orientation) of the upper frame 102 with respect to thebase frame 101, driving upper frame 102 towards a position within anorientation reference range. Similarly, increasing or decreasing a speedof the actuator adjusts the angular orientation of the upper frame 102with respect to the base frame 101, driving upper frame 102 towards aposition within an orientation reference range.

In step 318, the electronic control unit receives adjusted first and/orsecond angular orientations with respective first and second actuatorsoperatively coupled to respective first and second ends 122, 120 of theperson support apparatus 10, 100 to obtain adjusted first and/or secondreadings indicative of the adjusted first and/or second angularorientations. In embodiments, the first and/or second angularorientations may be calibrated and corrected based on the inclinometerangle received in step 302. In alternative embodiments, the PIDcontroller value is output to determine the adjusted first and/or secondreadings, such as in a situation where the readings are adjusted in abackground simulation tool to obtain simulated adjusted first and/orsecond readings within the fine orientation reference range prior to anactual actuation of respective foot and/or head actuators 111 and 113based on the obtained simulated adjusted first and/or second readingsthat are within the fine orientation reference range.

In step 320, in some embodiments, the electronic control unit comparesthe adjusted first and/or second readings with the fine orientationrange. When the adjusted first and/or second readings are outside of therespective fine orientation reference range, the method 300 proceeds tostep 322 to repeat steps 314 to 320 until the adjusted first and/orsecond readings are within the respective fine orientation referencerange. When in step 320 it is determined that the adjusted first and/orsecond readings are within the respective fine orientation referencerange, the method 310 proceeds to step 310 to continue using the footand/or head actuators 111, 113 to move the upper frame 102 of the personsupport apparatus 10, 100 in an upwards or downwards direction(indicated by arrow 600) until a desired position is achieved (e.g.,when a user ceases hilo movement of the person support apparatus).

In embodiments, the output PID controller value is looped via a loopingalgorithm, for example, to act as input values of simulated or actualpotentiometer angular readings into a PID controller loop to adjust thePID controller value output until it is within (and to maintain itwithin) a predetermined error range. While the present disclosuredescribes a methodology adjusting the PID controller value output untilit is within (and to maintain it within) a predetermined error range,for example, it should be understood that the PID controller valueoutput may be adjusted to minimize a difference or error betweenmeasured output values and a predetermined error-basis value reflectinga predetermined angular orientation that would allow for distribution ofthe fluidized particulate material within the bladder portion 110, andwhich predetermined error-basis value would be within the predeterminederror range.

The present disclosure describes a methodology of incorporating, forexample, a control feedback loop to assist with movement of a personsupport apparatus 10, 100 such that the fluidized particulate materialremains at a predetermined distribution within the bladder portion 110during such movement, for example. In embodiments, physical use of theactuators to correct the angular orientations of the person supportapparatus 10, 100 to be within the orientation reference range asdescribed herein may occur when the person support apparatus 10, 100happens to be at a level or position where the fluidized particulatematerial in the bladder portion 110 is not at a predetermineddistribution within the bladder portion 110 and is to be adjusted toachieve the predetermined distribution, which may occur prior to orduring the person support apparatus 10, 100 being moved in an upwards ordownwards direction (indicated by arrow 600) in a hilo movement.

In embodiments, a caregiver may adjust the person support apparatus 10,100 by use of a GUI on the control box 24, as described herein, wherethe caregiver is only permitted to make such adjustments that are withina restricted, preset range as found and controlled by the PID controlleroutputs of PID controllers PID1 and/or PID2. Thus, movement of theperson support apparatus may be limited such that when the caregiverprovides an instruction via the GUI, the adjustment only occurs after alooping algorithm has determined stroke lengths for one or bothactuators 111, 113 that place the adjustment within an orientationreference range. In embodiments, adjusting the first and/or secondangular orientations may include using at least one of operation of asemi-manual control and an automatic control. In embodiments, theoperation may include, for example, controlling one of an upwards anddownwards movement of the person support apparatus 10, 100 with at leastone of the foot and/or head actuators 111, 113. Adjusting at least oneof the first and second angular orientations may include the electroniccontrol unit outputting a stroke length signal that determines a strokelength for a respective foot and/or head actuators 111, 113. The atleast one of the first and second angular orientations of the respectivefoot and head ends 120, 122 of the person support apparatus 10, 100 maybe adjusted by an amount proportional to the stroke length.Alternatively, the operation may include, for example, a caregiverinputting a first value on the GUI, and, when the first value is withinthe orientation reference range or the fine orientation reference range,the electronic control unit outputs a stroke length signal based on thefirst value and for a first stroke length associated with the firstmotor M1. The angular orientation of the head end 122 of the personsupport apparatus 10, 100 is adjusted by an amount proportional to thefirst stroke length. In embodiments, the operation may further includeinputting a second value on the GUI, and, when the second value iswithin the orientation reference range or the fine orientation referencerange, the electronic control unit outputs a stroke length signal basedon the second value and for a second stroke length associated with thesecond motor M2. The angular orientation of the foot end 120 of theperson support apparatus 10, 100 is adjusted by an amount proportionalto the first stroke length.

In some embodiments, a caregiver may input adjustments to control one orboth of motors M1, M2 to actuate angular orientation movements ofrespective portions of the person support apparatus 10, 100 that remainwithin the coarse or fine orientation reference range and maintain apredetermined distribution of the fluidized particulate material withinthe bladder portion 110. Thus, the caregiver would not be able to inputadjustments that would lead to a distribution of the fluidizedparticulate material outside of the predetermined distribution or whichwould lead to a bottoming out of the fluidized particulate materialwithin the bladder portion 110. For example, only motor M1 may beadjusted to adjust the angular orientation of a first portion of theperson support apparatus 10, 100 with respect to a stationary secondportion of the person support apparatus to maintain or cause apredetermined distribution of the fluidized particulate material layerwithin the bladder portion 110 during hilo movement of the personsupport apparatus 10, 100. Or only motor M2 may be adjusted to adjustthe angular orientation of a second portion of the person supportapparatus 10, 100 with respect to a stationary first portion of theperson support apparatus to maintain or cause a predetermineddistribution of the fluidized particulate material layer within thebladder portion 110 during hilo movement (indicated by arrow 600) of theperson support apparatus 10, 100. The first end may be one of the headend 122 or the foot end 120 of the person support apparatus 100, and thesecond end may be the other of the head end 122 or the foot end 120 ofthe person support apparatus 100. It is contemplated within thisdisclosure that multiple actuators at varying positions, portions, orends of the person support apparatus 10, 100 may be used with thelooping algorithm of this disclosure to maintain the fluidizedparticulate material as a distributed layer within the bladder portion110.

In embodiments, a difference between the adjusted first and secondreadings may be within a range of from about +0.1° to about −0.5°. Inembodiments, a difference between the adjusted first and second readingsmay be within a range of from about +0.65° to about −0.15°. Inembodiments, a difference between the adjusted first and second readingsmay be within a range of from about +0.75° to about −0.75°. When thedifference between the adjusted first and second readings is negative,and the first portion is a head end and the second portion is a foot endof the person support apparatus 10, 100, the head end is disposed belowthe foot end in a trendelenburg position or direction of the personsupport apparatus 10, 100. When the difference between the adjustedfirst and second readings is positive, and the first portion is a headend and the second portion is a foot end of the person support apparatus10, 100, the head end is disposed above the foot end in a reversetrendelenburg position or direction of the person support apparatus 10,100.

In embodiments, when the head actuator 113 starts, it is incremented ata first duty cycle speed that may be, for example, a 10%pulse-width-modulation duty cycle speed. In embodiments, when the headactuator 113 starts and the foot actuator 111 starts, the head actuator113 may be incremented at a first duty cycle speed that may be at leastdouble a second duty cycle speed at which the foot actuator 111 isincremented. For example, the head actuator 113 may be incremented at a10% pulse-width-modulation duty cycle speed, and the foot actuator 111may be incremented at a 5% pulse-width-modulation duty cycle speed. Inembodiments, drives such as actuators 111, 113 may start initially at agreater speed than they are later incremented by to correct for startingerror, and one actuator, such as the head actuator 113 may start 200 msbefore the other actuator, such as the foot actuator 111. If adifference between first and/or second readings of respectivepotentiometers P1, P2 is zero within the resolution of the angularvalues or orientations, actuators 111, 113 may start at different times,or only one of actuators 111 and 113 may start. Alternatively, actuators111, 113 may start at the same time. In embodiments, the method 300 maybe employed from steps 302 to 306 to conduct a calibration based on aninclinometer I reading. And, after the actuators 111 and/or 113 start,the method 300 continues on to employ steps 308 to 314 such that a PIDalgorithm uses potentiometer readings during a hilo movement of theperson support apparatus 10, 100, for example, to avoid a response delaythat may otherwise occur due to a calibration step that was notundertaken before the actuators 111 and/or 113 started.

As noted herein, the depth of the fluidized particulate material in themattress system may vary depending on the angular orientation of theupper frame 102 of the person support apparatus 10, 100. It has alsobeen found that the depth of the particulate material may vary dependingon the angular orientation of the torso frame 109 with respect to thebase frame 101, increasing the risk of bottoming out. For example, for aperson of a given weight positioned on the person support apparatus 10,100, increasing the angle of inclination of the torso frame 109 causes agreater displacement of the particulate material from beneath theperson. It has now been determined that the angular orientation of theupper frame 102 can be adjusted based on the angular orientation of thetorso frame 109 and the weight of the person disposed on the personsupport apparatus 10, 100 to ensure that sufficient particulate materialis disposed beneath the person, thereby mitigating the risk of bottomingout.

Referring now to FIGS. 7A, 10-14 and Tables 1-2 of FIGS. 15-16, exampledata is presented from a trial study that included six text subjectshaving weights varying from 117 to 350 lbs. The depth of immersion ofeach subject in the fluidized bed 112 was measured at the line 700 (FIG.7A) for different head-of-bed (HOB) angles. The HOB angle corresponds tothe angular orientation of the torso frame 109 (FIGS. 1 and 6) relativeto the upper frame 102. The line 700 generally corresponds to theposition of each subject's sacrum (i.e., the subject's lowerback/gluteus muscles) on the mattress system and, hence, the point ofmaximum immersion in the fluidized bed. A length L is illustrated inFIG. 7A and extends from line 700 to the foot end of the fluidized bed(as measured from the interior of the tub portion) and indicates thepoint of maximum immersion. Depth of immersion measurements wereconducted for each subject at different HOB angles for a total of 10trials at HOB angles of 0°, 30°, 45°, and 60° to determine a maximumimmersion of each subject's sacrum within the fluidized particulatematerial. Referring to FIG. 10, FIG. 10 graphically depicts theimmersion depth (y-axis, in inches) as a function of weight (x-axis, inlbs.) for various HOB angles. The data in FIG. 10 generally indicates alinear relationship between HOB angle, person weight, and depth ofimmersion. For example, for a given weight, an individual tends to beimmersed to a greater depth within the fluidized particulate material attheir sacrum, which depth of immersion increases as the HOB angleincreases. This relationship is generally consistent for each weight,though a heavier person will be immersed to a greater depth than alighter person at any given HOB angle. For example, FIG. 10 shows fourseparate linear relationships at four respective HOB angles 0°, 30°,45°, and 60°. A person of 350 lbs. would, for example, be immersed toabout 8.1 inches at an HOB angle of 0°, be immersed to about 8.55 inchesat an HOB angle of 30°, be immersed to about 8.8 inches at an HOB angleof 45°, and be immersed to about 9.25 inches at an HOB angle of 60°. Alighter person of about 150 lbs. would have a similar increase of thedepth of immersion at each increasing HOB angle, though the lighterperson would be immersed to a lesser depth. For example, a person of 150lbs. would be immersed to about 6.5 inches at an HOB angle of 0°, beimmersed to about 7.1 inches at an HOB angle of 30°, be immersed toabout 7.5 inches at an HOB angle of 45°, and be immersed to about 7.9inches at an HOB angle of 60°.

FIGS. 11-14 illustrate separate regression analysis studies of immersion(x-axis, in inches) versus weight (y-axis, in lbs.) for HOB angles of0°, 30°, 45° and 60° based on the data from FIG. 10. For example, FIG.11 is a graphical depiction of a regression analysis of immersion versusperson weight at an HOB angle of 0°, indicating a generally linearrelationship between weight and depth of immersion. Assuming that anundesired migration of the fluidized particulate material and bottomingoccurs at approximately 9 inches of immersion, extension of thegenerally linear relationship line of FIG. 11 (which has a slope ofabout 107.3 lbs./inch) indicates a maximum supportable weight ofapproximately 420 lbs. before bottoming occurs (at 9 inches). FIG. 12similarly is a graphical depiction of a regression analysis of immersionversus person weight at an HOB angle of 30°, and extension of thegenerally linear relationship line of FIG. 12 (which has a slope ofabout 96.7 lbs./inch) indicates a maximum supportable weight ofapproximately 359 lbs. before bottoming occurs (at 9 inches). Further,FIG. 13 is a graphical depiction of a regression analysis of immersionversus person weight at an HOB angle of 45°, and extension of thegenerally linear relationship line of FIG. 13 (which has a slope ofabout 96.2 lbs./inch) indicates a maximum supportable weight ofapproximately 320 lbs. before bottoming occurs (at 9 inches). Similarly,FIG. 14 is a graphical depiction of a regression analysis of immersionversus person weight at an HOB angle of 60°, and extension of thegenerally linear relationship line of FIG. 14 (which has a slope ofabout 113.3 lbs./inch) indicates a maximum supportable weight ofapproximately 280 lbs. before bottoming occurs (at 9 inches). Thus,FIGS. 11-14 illustrate that a higher HOB angle generally results in areduction of the maximum weight that is supportable before there isinsufficient fluidized particulate material below the subject andbottoming occurs.

As noted herein, it has been determined that the angular orientation ofthe upper frame 102 can be adjusted based on the angular orientation ofthe torso frame 109 and the weight of the person disposed on the personsupport apparatus 10, 100 to ensure that sufficient particulate materialis disposed beneath the person, thereby mitigating the risk ofbottoming. Specifically, it has been found that by orienting the upperframe relative to the base frame such that the foot end of the upperframe is at a higher elevation than the head end of the support framecan increase the maximum supportable weight of the person supportapparatus irrespective of the HOB angle, as indicated by the followingmodeled examples. Specifically, Comparative Example 1 and InventiveExample 2 below are based on modeled data derived from the regressionanalyses graphically depicted in FIGS. 11-14.

COMPARATIVE EXAMPLE 1

Referring now to TABLE 1 presented in FIG. 15, TABLE 1 includes thechange (decrease) in the depth of the particulate material (ΔDepth, ininches) and the corresponding change (decrease) in the maximumsupportable weight (ΔSupport, in lbs.) as a function of the change inangle of orientation (Δθ, in degrees (°)) of the upper frame withrespect to the base frame. In this example, the initial angle betweenthe upper frame and the base frame is unbiased (i.e., 0°) and, hence,the maximum supportable weights for each condition are the same as thosedescribed above with respect to FIGS. 11-14. The change in the angle AOpresented in TABLE 1 corresponds to the foot end of the upper framebeing oriented at a lower elevation than the head end of the supportframe. The modeled data assumes an initial bottoming depth of 9 inchesfor each weight and a sacrum position of 40 inches (i.e., L=40 inches)from the foot end of the fluidized bed (as measured from the interior ofthe tub portion). The data are presented for HOB angles of 0°, 30°, 45°,and 60°.

The data in TABLE 1 generally indicates that as AO increases, the depthof the particulate material under the sacrum of the subject decreases.This decrease in the depth of the particulate material yields acorresponding decrease in the maximum weight which can be supported onthe mattress system of the person support apparatus without bottoming.This trend is consistent for each HOB angle modeled.

As an example, for an HOB angle of 30°, as described above with respectto FIG. 12, bottoming would occur at a maximum supportable weight of 359lbs when the angle θ is 0°. However, as the angle θ increases, themaximum supportable weight decreases. For example, at a seat above footbed tilt angle of 0.5°, the change (decrease) in the maximum supportableweight is 33.8 lbs. (i.e., ΔSupport is 33.8 lbs.) Thus, the new maximumsupportable weight would be 359 lbs less 33.8 lbs, or 325.2 lbs.

INVENTIVE EXAMPLE 2

A second model was developed similar to the model of ComparativeExample 1. However, in contrast to Comparative Example 1, in thisexample the initial angle between the upper frame and the base frame wasbiased. Specifically, the head end of the support frame was modeled tohave a lower elevation than the foot end of the support frame such thatthe angle between the support frame and the base frame was −0.25° (headbelow foot). In this orientation the particulate material had a greaterdepth under the sacrum of the subject and, hence, the maximumsupportable weights increased relative to Comparative Example 1. Thatis, in Inventive Example 2, the maximum supportable weights wereinitially 439 lbs., 376 lbs., 336 lbs., and 299 lbs. owing to theinitial bias angle.

Further, as in Comparative Example 1, in Inventive Example 2 it wasfound that as AO increases, the depth of the particulate material underthe sacrum of the subject also decreases. This decrease in the depth ofthe particulate material yields a corresponding decrease in the maximumweight which can be supported on the mattress system of the personsupport apparatus without bottoming. This trend is consistent for eachHOB angle modeled. However, the overall maximum supportable weight foreach condition modeled in Inventive Example 2 was generally greater thanthe maximum supportable weight for the same condition of ComparativeExample 1 owing to the initial bias angle.

Thus, based on Inventive Example 2, the angle of the upper frame withrespect to the base frame can be adjusted to increase the maximumsupportable weight of the person support apparatus thereby reducing therisk of bottoming. Moreover, to ensure that the risk of bottoming ismitigated for a specific person supported on the person supportapparatus, the angle of the upper frame with respect to the base framecan be adjusted based on the weight of the person as well as the HOBangle.

Specifically, an angle between the upper frame and the support framethat mitigates the risk of bottoming can be determined based on theweight of the person and the HOB angle utilizing the regression modelsgraphically depicted in FIGS. 10-14. Referring to TABLE 2 of FIG. 16, amean slope may be determined based on the four linear relationships foreach respective HOB angle of 0°, 30°, 45°, and 60° as set forth in FIGS.10-14. As noted herein, FIG. 10 graphically depicts the four linearrelationships plotted on the same axes, and FIGS. 11-14 graphicallyrepresent weight (in pounds) as a function of depth of immersion (ininches) according to the specified equations for each HOB angle modeled.For example, FIG. 11 plots a linear relationship associated with an HOBangle of 0° according to the following equation:Weight=107.29*Immersion−550.93. FIG. 12 plots a linear relationshipassociated with an HOB angle of 30° according to the following equation:Weight=96.771*Immersion−517.49. FIG. 13 plots a linear relationshipassociated with an HOB angle of 45° according to the following equation:Weight=96.217*Immersion−543.99. Further, FIG. 14 plots a linearrelationship associated with an HOB angle of 60° according to thefollowing equation: Weight=113.35*Immersion−732.01. The lines associatedwith these equations may be manipulated to derive the depth of immersionas a function of weight according to the relationship y=mx+b for eachHOB angle (i.e., 0°, 30°, 45°, and 60°), where y is the depth, m is theslope of the line in the corresponding figure, x is the weight of thesubject, and b is the y intercept. These equations are set forth inTABLE 2, presented in FIG. 16, for each HOB angle of 0°, 30°, 45° and60°. The derived slopes of TABLE 2 can be averaged to determine a meanslope of 0.00972 inches per pound. As the equations are derived from thegenerally parallel linear relationships plotted in FIG. 10 that differprimarily with respect to an intercept, the information from TABLE 2 maybe combined into an equation for depth of immersion and a regressionperformed to determined the intercept coefficient for the equation whileusing the determined mean slope as a weight coefficient (or rather aconstant multiplier for the weight variable in the equation). Theintercept is determined via the regression as a function of the HOBangle. The intercept coefficient was determined to be 4.9654 inches andthe HOB coefficient was determined to be 0.02025 inches per degree.EQUATION 1 below sets forth the following derived equation (includingunits in parentheses) in which depth of immersion is a function ofweight and HOB angle:Depth of Immersion (inches)=0.00972 (inches/lb.)*Weight (lbs.)+0.02025(inches/degree)*HOB angle (degrees)+4.9654 (inches)  EQUATION 1

Based on the foregoing, it should be understood that EQUATION 1 may beutilized to determine the depth of immersion of a person in theparticulate material based on the weight of the person and the HOBangle. For example, TABLE 3 of FIG. 17 includes the calculated depth ofimmersion utilizing EQUATION 1 for different weights and HOB anglesbased on EQUATION 1. Those calculations were then compared to the depthmeasurements from the regressions (i.e., FIGS. 10-14 which are derivedfrom empirical data) to determine an error value. As shown in TABLE 3,the error ranges are generally less than 2% indicating good agreementbetween the empirically derived data and the calculated data. Forexample, for a weight of 200 pounds at an HOB angle of 30°, EQUATION 1results in a calculated depth of 6.898 inches. The empirical data fromthe regressions based on these variables is 7 inches, indicating arelatively small error of 1.47% between the calculated and regressiondata.

EQUATION 1 can be further modified to account for an additional, offsetminimum immersion depth (i.e., an offset depth) to ensure a certainamount of particulate material is present beneath the sacrum of theperson. Thus, EQUATION 1 can be rewritten as a target depth of immersionas follows:Target Depth of Immersion (inches)=0.00972 (inches/lb.)*Weight(lbs.)+0.02025 (inches/degree)*HOB angle (degrees)+4.9654(inches)+offset minimum immersion depth (inches)  EQUATION 2

The offset minimum immersion depth may be, for example, 1 inch. However,it should be understood that the offset minimum immersion depth may begreater than or less than 1 inch. In some embodiments, the offsetminimum immersion depth may be zero.

The Target Depth of Immersion may be related to a Nominal Depth ofImmersion plus L*sin θ to establish a relationship between the tiltangle θ of the upper frame with respect to the base frame and the depthof immersion. Specifically:Target Depth of Immersion (inches)=Nominal Depth (inches)+L*sinθ  EQUATION 3

where L is the sacrum position as measured from the foot end of thefluidized bed (from the interior portion of the tub portion as depictedin FIG. 7A) and θ is the tilt angle between the upper frame and the baseframe such that the head end of the upper frame is positioned lower thanthe foot end of the support frame. In embodiments, the nominal depth isan assumed constant such as 9 inches depth of immersion, for example,that may or may not include a reference position tilt in a trendelenburgdirection.

Based on EQUATION 2, EQUATION 3 can be rewritten as follows:Nominal Depth (inches)+L*sin θ=0.00972 (inches/lb.)*Weight(lbs.)+0.02025 (inches/degree)*HOB angle (degrees)+4.9654(inches)+offset minimum immersion depth (inches)  EQUATION 4

EQUATION 4 can then be solved for the tilt angle θ such that:θ=(1/L)*sin⁻¹ (0.00972 (inches/lb.)*Weight (lbs.)+0.02025(inches/degree)*HOB angle (degrees)+4.9654 (inches)+offset minimumimmersion depth (inches)−Nominal Depth (inches))  EQUATION 5

Thus, the tilt angle θ between the upper frame and the base frame can bedetermined based on the weight of the person and the HOB angle usingEQUATION 5 to ensure that there is sufficient particulate material(i.e., at least a minimum depth of particulate material) under thesacrum of the person to mitigate bottoming. More specifically, once thetilt angle θ has been determined, the angle between the upper frame withrespect to the base frame can be adjusted to the tilt angle θ therebycausing particulate material in the fluidized bed to accumulate beneaththe sacrum of the person, reducing the risk of bottoming. Inembodiments, the tilt angle θ may be from greater than or equal to 0°and less than or equal to 10.1°. When the tilt angle θ is greater than0°, the upper support frame is oriented such that a head end of theframe is lower than the foot end (i.e., head below foot). Inembodiments, determining the tilt angle of the upper frame with respectto the base frame may include calculating the tilt angle according tothe following equation, which is a simplified version of EQUATION 5:θ=(1/L)*sin⁻¹(MD−ND)  EQUATION 6

With respect to EQUATION 6, θ is the tilt angle, L is indicative of alength between the foot end of the bladder portion and the point ofmaximum immersion depth, MD is the minimum depth of the fluidizedparticulate material, and ND is a nominal depth of the fluidizedparticulate material. Specifically, MD is the minimum depth of thefluidized particulate material as determined through EQUATION 2, orrather MD=0.00972 (inches/lb.)*Weight (lbs.)+0.02025 (inches/degree)*HOBangle (degrees)+4.9654 (inches)+offset minimum immersion depth (inches),where the offset minimum immersion depth may be zero. In embodiments,the minimum depth includes an offset value (e.g., an additional minimumimmersion depth of 1 inch).

Accordingly, it should be understood that in some embodiments describedherein the orientation of the upper frame with respect to the base framemay be adjusted based on the weight of the patient and, optionally, theHOB angle in order to mitigate bottoming. Referring now to FIGS. 1-2 and7A-7D, by way of example, in some embodiments, the control box 24 of theperson support apparatus 10 receives a signal from the load beams and/orload cells disposed in the base frame 101 of the person supportapparatus 10 indicative of the weight of the person positioned on theperson support apparatus 10. In addition, the control box 24 receives asignal from an orientation sensor operatively associated with the torsosupport section 91 of the person support apparatus 10 indicative of theHOB angle (i.e., the angle between the upper frame 102 and the torsoframe 109 and/or deck 94). Based on these signals, the control box 24determines an appropriate tilt angle θ between the upper frame 102 andthe base frame 101 such that there is sufficient particulate material inthe fluidized bed 112 at the line 700 to prevent the person frombottoming. The tilt angle thus corresponds to a minimum depth of thefluidized particulate material at a point of maximum immersion of theperson on the bladder portion 110 of the support surface of the personsupport apparatus 10. For example, in embodiments, the control box 24may include a look up table (LUT) of values for the tilt angle θ indexedaccording to the weight of the person positioned on the person supportapparatus 10 and the HOB angle. In other embodiments, the control box 24may directly calculate the tilt angle θ from, for example, EQUATION 5 orEQUATION 6 described hereinabove.

While the control box 24 has been described herein as receiving signalsindicative of the weight of the person and the HOB angle from respectivesensors associated with the person support apparatus 10, it should beunderstood that other embodiments are contemplated and possible. Forexample, in embodiments, a user, such as a caregiver, may directly inputthe weight of the person and/or the HOB angle into the control unitusing, for example, the GUI of the control box or a related controller(e.g., a pendant controller or the like).

Still referring to FIGS. 1-2 and 7A-7D, once the control box 24 hasdetermined the appropriate tilt angle θ, the control box 24 actuates thefoot actuator 111 and/or the head actuator 113 such that the upper frame102 is oriented at the tilt angle θ with respect to the base frame 101(i.e., adjusting an angular orientation of the upper frame 102 withrespective to the base frame 101 until the upper frame 102 is orientedat the tilt angle θ with respect to the base frame 101). As notedhereinabove, when the upper frame 102 is oriented at the tilt angle θwith respect to the base frame 101, the foot end 120 of the upper frame102 is positioned at a higher elevation than the head end 122 of theupper frame 102 thereby causing particulate material in the fluidizedbed 112 to accumulate in the bladder portion 110 proximate the line 700,providing the minimum depth of fluidized particulate material to preventbottoming out at the maximum immersion point.

Thus, through the methods and apparatuses described herein, a caregiverand/or person support apparatus 10, 100 may maintain a tilt angle of thebladder portion 110 from a foot end 120 to a head end based 122 on aperson's weight and an HOB angle of the torso frame 109 to maintain apredetermined distribution of the fluidized particulate material withinthe bladder portion 110 of the person support apparatus 100. Further,through the methods and apparatuses described herein, a caregiver and/orperson support apparatus 100 may maintain a predetermined distributionof the fluidized particulate material within the bladder portion 110 ofthe person support apparatus 100 while the person support apparatus 100is being adjusted either by moving upwards or downwards and/or havingits angular orientation changed. By maintaining a distribution of thefluidized particulate material within the bladder portion 110 duringsuch movement and adjustment of the person support apparatus 100, forexample, a protective cushion provided by the fluidized particulatematerial is maintained within the bladder portion 110 beneath the personresting on the person support apparatus 100. Maintaining such aprotective cushion prevents bottoming that could be otherwise be causedby a migration of the fluidized particulate material to the foot end 122of the person support apparatus 100 when the angular orientation of theperson support apparatus 100 is beyond a predetermined range.

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue.

While particular embodiments have been illustrated and described herein,it should be understood that various other changes and modifications maybe made without departing from the spirit and scope of the claimedsubject matter. Moreover, although various aspects of the claimedsubject matter have been described herein, such aspects need not beutilized in combination. It is therefore intended that the appendedclaims cover all such changes and modifications that are within thescope of the claimed subject matter.

What is claimed is:
 1. A method for controlling an angular orientationof a person support apparatus including a support surface having abladder portion containing fluidized particulate material configured formigration within the bladder portion along a bottom surface of thebladder portion due to a gravitational pull toward an end of the personsupport apparatus, an upper frame, and a base frame, the methodcomprising: adjusting a height of the upper frame with respect to thebase frame with at least one of a first actuator and a second actuatorat respective first and second actuator speeds; determining a dynamicangular orientation of the upper frame with respect to the base framebased on at least one of an operating characteristic of the firstactuator and an operating characteristic of the second actuator;determining a corrected angular orientation based on the dynamic angularorientation and a floor angle, wherein the floor angle is indicative ofan orientation of the base frame sensed with respect to horizontal andis generated as a sensed output estimation; comparing the correctedangular orientation with an orientation reference range, within whichorientation reference range the fluidized particulate material maintainsa predetermined depth distribution within the bladder portion to preventbottoming out, the predetermined depth distribution comprising a layerof fluidized particulate material disposed on the bottom surface of thebladder portion with a first depth at a first end of the bladder portionand a second depth different from the first depth at a second end of thebladder portion such that an angle between the first depth and thesecond depth is within the orientation reference range; and adjusting atleast one of the first actuator speed and the second actuator speed whenthe corrected angular orientation is outside the orientation referencerange until the corrected angular orientation is within the orientationreference range.
 2. The method of claim 1, wherein the fluidizedparticulate material contained within the bladder portion of the personsupport apparatus has the predetermined depth distribution in thebladder portion when the corrected angular orientation is within theorientation reference range.
 3. The method of claim 1, furthercomprising an initial step of determining the floor angle indicative ofthe orientation of the base frame with respect to horizontal based on avalue generated from an inclinometer disposed on the person supportapparatus.
 4. The method of claim 1, wherein at least one of the firstactuator speed and the second actuator speed are adjusted and thedynamic angular orientation is determined as the upper frame transitionswith respect to the base frame from a first height to a second height.5. The method of claim 4, wherein the dynamic angular orientation isdetermined at least partially based on one or more values generated fromat least one of a first potentiometer associated with the first actuatorand a second potentiometer associated with the second actuator.
 6. Themethod of claim 1, wherein: the orientation reference range is measuredrelative to a reference position of the person support apparatus; andthe reference position is at 0.25° such that the person supportapparatus is oriented with a foot end of the person support apparatushigher than a head end.
 7. The method of claim 1, wherein: theorientation reference range is measured relative to a reference positionof the person support apparatus; and the reference position is in arange from about +0.1° to about −0.5° such that the person supportapparatus is oriented with a foot end of the person support apparatushigher than a head end when the reference position is in a negative endof the range.
 8. The method of claim 1, wherein: the orientationreference range is measured relative to a reference position of theperson support apparatus; and the orientation reference range is in atleast one of the following ranges relative to the reference position: arange from about −0.4 to about +0.4° relative to the reference position;and a range from about −0.25° to about +0.25° relative to the referenceposition.
 9. A method for controlling an angular orientation of a personsupport apparatus that includes a support surface having a bladderportion containing fluidized particulate material configured formigration within the bladder portion along a bottom surface of thebladder portion due to a gravitational pull toward an end of the personsupport apparatus, the method comprising: actuating at least one of afirst actuator and a second actuator, respectively coupled to the personsupport apparatus at a first end and a second end, at a respective firstactuator speed and a second actuator speed to raise or lower a height ofthe person support apparatus; receiving a first reading indicative of afirst angular orientation of the first end of the person supportapparatus with respect to the second end and relative to horizontal,wherein the first reading is at least generated from a first sensor anda second sensor respectively associated with the first actuator and thesecond actuator; determining a corrected first reading indicative of thefirst angular orientation based on the first reading and a calibrationof the person support apparatus configured to generate a sensed outputestimation of an orientation of the person support apparatus withrespect to horizontal; comparing the corrected first reading and anorientation reference range within which orientation reference range thefluidized particulate material maintains a predetermined depthdistribution within the bladder portion to prevent bottoming out, thepredetermined depth distribution comprising a layer of fluidizedparticulate material disposed on the bottom surface of the bladderportion with a first depth at a first end of the bladder portion and asecond depth different from the first depth at a second end of thebladder portion such that an angle between the first depth and thesecond depth is within the orientation reference range; and actuating atleast one of the first actuator and the second actuator automatically ata different speed when the corrected first reading is outside theorientation reference range until an adjusted corrected first readingindicative of an adjusted first angular orientation is within theorientation reference range.
 10. The method of claim 9, wherein thefluidized particulate material contained within the bladder portion ofthe person support apparatus has the predetermined depth distribution inthe bladder portion when the corrected first reading is within theorientation reference range.
 11. The method of claim 9, wherein: thefirst end comprises a foot end; the second end comprises a head end; andthe orientation reference range is measured relative to a referenceposition of the person support apparatus; and the reference position isat 0.25° such that the person support apparatus is oriented with thefoot end of the person support apparatus higher than the head end. 12.The method of claim 9, wherein the orientation reference range is in arange from about −0.4° to about +0.4° relative to a reference position.13. The method of claim 9, further comprising calibrating the personsupport apparatus to generate the calibration, the calibratingcomprising: calculating, automatically with an inclinometer, a floorangle associated with the person support apparatus relative tohorizontal to generate the sensed output estimation of the orientationof the person support apparatus with respect to horizontal.
 14. Themethod of claim 9, wherein: the first reading is generated from at leastone of a first potentiometer associated with the first actuator and asecond potentiometer associated with the second actuator; and the methodfurther comprises calibrating the person support apparatus to generatethe calibration, the calibrating comprising calculating, automaticallywith an inclinometer, a floor angle associated with the person supportapparatus relative to horizontal; and determining the corrected firstreading comprises calculating the corrected first reading based on thefirst reading and the floor angle.
 15. The method of claim 14, furthercomprising: receiving input from at least one of the first potentiometerand the second potentiometer respectively in at least one of a first PIDcontroller and a second PID controller; outputting at least one of afirst actuator drive signal from the first PID controller and a secondactuator drive signal from the second PID controller; and repeating thereceiving and outputting steps until the adjusted corrected firstreading indicative of the adjusted first angular orientation is withinthe orientation reference range.
 16. The method of claim 9, wherein: thefirst reading is at least partially generated from a first potentiometerassociated with the first actuator and a second potentiometer associatedwith the second actuator; and actuating at least one of the firstactuator and the second actuator comprises outputting a stroke lengthsignal related to a stroke length for the respective first and secondactuators, wherein the stroke length of the first actuator is an inputwith respect to the first potentiometer and the stroke length of thesecond actuator is an input with respect to the second potentiometer.17. The method of claim 16, further comprising: receiving the respectivestroke lengths for the first and second actuators associated with thecorrected first reading as a respective input in at least one of a firstPID controller and a second PID controller; outputting at least one of afirst actuator drive signal from the first PID controller and a secondactuator drive signal from the second PID controller; and repeating thereceiving and outputting steps until the adjusted corrected firstreading indicative of the adjusted first angular orientation is withinthe orientation reference range.
 18. The method of claim 9, wherein thefirst actuator is incremented at a first duty cycle speed that is atleast double a second duty cycle speed at which the second actuator isincremented.
 19. The method of claim 18, wherein the first duty cyclespeed is at a 10% pulse-width-modulation and the second duty cycle speedis at a 5% pulse-width-modulation.
 20. A system for controlling anangular orientation of a person support apparatus that includes asupport surface having a bladder portion containing fluidizedparticulate material configured for migration within the bladder portionalong a bottom surface of the bladder portion due to a gravitationalpull toward an end of the person support apparatus, the systemcomprising: at least a first actuator associated with a head end as afirst end and a second actuator associated with a foot end as a secondend of the person support apparatus; and an electronic control unitcomprising a processor communicatively coupled to a non-transitorycomputer storage medium, wherein the non-transitory computer storagemedium stores instructions that, when executed by the processor, causethe processor to: actuate at least one of the first actuator and thesecond actuator at a respective first actuator speed and a secondactuator speed to raise or lower a height of the person supportapparatus; receive, automatically with the electronic control unit, afirst reading indicative of a first angular orientation of the first endof the person support apparatus with respect to the second end andrelative to horizontal, wherein the first reading is generated from afirst sensor and a second sensor respectively associated with the firstactuator and the second actuator; determine, automatically with theelectronic control unit, a corrected first reading indicative of thefirst angular orientation based on the first reading and a calibrationof the person support apparatus configured to generate a sensed outputestimation of an orientation of the person support apparatus withrespect to horizontal; compare, automatically with the electroniccontrol unit, the corrected first reading and an orientation referencerange, within which orientation reference range the fluidizedparticulate material maintains a predetermined depth distribution withinthe bladder portion to prevent bottoming out, the predetermined depthdistribution comprising a layer of fluidized particulate materialdisposed on the bottom surface of the bladder portion with a first depthat a first end of the bladder portion and a second depth different fromthe first depth at a second end of the bladder portion such that anangle between the first depth and the second depth is within theorientation reference range; and actuate at least one of the firstactuator and the second actuator, automatically with the electroniccontrol unit, at a different speed when the corrected first reading isoutside the orientation reference range until an adjusted correctedfirst reading indicative of an adjusted first angular orientation iswithin the orientation reference range.